Ligand compound, chromium compound and catalyst system including the same

ABSTRACT

The present invention relates to a ligand compound, a chromium compound, and a catalyst system including the same. The catalyst system including the ligand compound or chromium compound according to the present invention exhibits high catalytic activity in ethylene oligomerization reaction, and therefore, polyethylene can be prepared using a small amount of comonomers or using only ethylene without comonomers.

This application is a National Stage Application of International PatentApplication No. PCT/KR2013/004158, filed on May 10, 2013, and claims thebenefit of Korean Patent Application Nos. 10-2012-0049712, filed on May10, 2012 and 10-2013-0052702, filed on May 9, 2013, in the KoreanIntellectual Property Office, all of which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a ligand compound, a chromium compound,and a catalyst system including the same. More particularly, the presentinvention relates to a novel ligand compound, chromium compound, andcatalyst system including the same which exhibit high activity forethylene oligomerization reaction.

This application claims the benefit of Korean Patent Application No.10-2012-0049712 on May 10, 2012 and Korean Patent Application No.10-2013-0052702 on May 9, 2013 with the Korean Intellectual PropertyOffice, the disclosure of which is herein incorporated by reference inits entirety.

BACKGROUND ART

Linear alpha-olefin is widely used in important commercial substancessuch as comonomers, detergents, lubricants, plasticizers or the like,and in particular, 1-hexene and 1-octene are commonly used as comonomersfor controlling density of polyethylene during preparation of linear lowdensity polyethylene (LLDPE).

In the conventional preparation process of LLDPE (Linear Low-DensityPolyethylene), copolymerization of ethylene with alpha-olefin, forexample, a comonomer such as 1-hexene and 1-octene is carried out inorder to control density by forming branches in the polymer backbone.

Therefore, there is a problem that the comonomer increases theproduction cost of LLDPE having a high content of comonomers. Manydifferent methods have been tried to solve this problem.

Further, because the application field or market size depends on thetype of alpha-olefin, a technique capable of selectively producing aparticular olefin is commercially important. Recently, many studies havebeen conducted on a chromium catalyst for preparing 1-hexene or 1-octenewith a high selectivity through selective ethylene oligomerization.

The conventional commercial method for 1-hexene or 1-octene preparationis the SHOP process of Shell Chemical, the Ziegler Process of ChevronPhilips, or the like, which is used to produce alpha-olefins having awide distribution range from C4˜C20 carbons.

Further, many studies have been conducted to selectively prepare1-hexene or 1-octene by ethylene trimerization or tetramerization usingan organic metal catalyst (J. Am. Chem. Soc 2003, 125, 5272, Ind. Eng.Chem. Res. 2008, 47, 5369, WO03/053890), but there is a still need forthe catalysts exhibiting a sufficiently high activity.

DISCLOSURE Technical Problem

In order to solve the above problems of the conventional technology, anobject of the present invention is to provide a novel ligand compoundand chromium compound which maintain high activity and thus are used inethylene oligomerization reaction so as to prepare low-densitypolyethylene in one reactor using a small amount of comonomers or usingonly ethylene without comonomers.

Further, another object of the present invention is to provide acatalyst system including the ligand compound or the chromium compound.

Technical Solution

In order to achieve the above objects, the present invention provides aligand compound represented by the following Chemical Formula 1.

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other,and each independently a hydrogen atom, a hydrocarbyl group having 1 to30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbonatoms.

Further, the present invention provides a chromium compound representedby the following Chemical Formula 2.

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other,and each independently a hydrogen atom, a hydrocarbyl group having 1 to30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbonatoms, and

X is a halogen atom or an alkyl group having 1 to 6 carbon atoms.

Further, the present invention provides a catalyst system including i)the ligand compound represented by Chemical Formula 1 and a chromiumsource, or ii) the chromium compound represented by Chemical Formula 2;and a cocatalyst.

Advantageous Effects

The catalyst system including the ligand compound or the chromiumcompound according to the present invention can be used in ethyleneoligomerization to oligomerize ethylene with a high catalytic activity,compared to the known catalyst system. That is, when a polyolefin ispolymerized using the catalyst system according to the presentinvention, highly active ethylene oligomerization reaction is possible,and therefore, it is possible to polymerize a low-density polyethylenein one reactor using only ethylene without injection of additionalcomonomers.

DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing the result of GC-MS of the products resultingfrom ethylene oligomerization reaction according to Example 4 of thepresent invention.

BEST MODE

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.The singular forms are intended to include the plural forms as well,unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “includes, “comprises,” or “has” when used inthis specification, specify the presence of stated features, integers,steps, components, or combinations thereof, but do not preclude thepresence or addition of one or more other features, integers, steps,components, or combinations thereof.

While the present invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample and will herein be described in detail. It should be understood,however, that these are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention.

Hereinafter, a ligand compound, a chromium compound, and a catalystsystem of the present invention will be described in detail.

Ligand Compound

The ligand compound of the present invention may be represented by thefollowing Chemical Formula 1.

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other,and each independently a hydrogen atom, a hydrocarbyl group having 1 to30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbonatoms.

As used herein, the hydrocarbyl group means a monovalent hydrocarbongroup, and the heterohydrocarbyl group means a monovalentheterohydrocarbon group containing carbon atom and one or moreheteroatoms.

According to one embodiment of the present invention, R₁, R₂, R₂′ and R₃are each independently a hydrogen atom, an alkyl group having 1 to 20carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an arylgroup having 6 to 14 carbon atoms, an alkylaryl group having 7 to 12carbon atoms, an arylalkyl group having 7 to 12 carbon atoms or analkoxyaryl group having 7 to 12 carbon atoms, but are not limitedthereto.

Preferably, R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, alinear alkyl group having 1 to 20 carbon atoms, an isopropyl group, atert-butyl group, an amyl group, a phenyl group, an alkylphenyl grouphaving 7 to 12 carbon atoms or an alkoxyphenyl group having 7 to 12carbon atoms, but are not limited thereto.

According to one embodiment of the present invention, the compoundrepresented by Chemical Formula 1 may be selected from the followingchemical structures, but the present invention is not limited thereto.

The compound represented by Chemical Formula 1 can be synthesized by thefollowing method, but is not limited thereto. The preparation method ofthe ligand compound represented by Chemical Formula 1 will be describedin detail in the following Examples.

The ligand compound represented by Chemical Formula 1 may furtherinclude the chromium source and the cocatalyst to be used in ethyleneoligomerization reaction. In particular, because highly active ethyleneoligomerization reaction is possible, low-density polyethylene can beprepared in one reactor using a small amount of comonomers or using onlyethylene without comonomers.

Chromium Compound

The chromium compound of the present invention may be represented by thefollowing Chemical Formula 2.

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other,and each independently a hydrogen atom, a hydrocarbyl group having 1 to30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbonatoms, and

X is a halogen atom or an alkyl group having 1 to 6 carbon atoms.

Detailed descriptions and preferred examples of R₁, R₂, R₂′, and R₃ arethe same as in the descriptions of the ligand compound of ChemicalFormula 1.

In Chemical Formula 2, X is a halogen atom or an alkyl group having 1 to6 carbon atoms, and specific examples thereof may include methyl, ethyl,propyl, isopropyl, t-butyl, iso-butyl or the like, but are not limitedthereto.

According to one embodiment of the present invention, X is preferably Clor a methyl group, and more preferably Cl.

According to one embodiment of the present invention, the chromiumcompound represented by Chemical Formula 2 may be selected from thefollowing chemical structures, but the present invention is not limitedthereto.

The chromium compound represented by Chemical Formula 2 can besynthesized by the following method, but is not limited thereto. Thepreparation method of the chromium compound represented by ChemicalFormula 2 will be described in detail in the following Examples.

In ethylene oligomerization reaction, the chromium compound representedby Chemical Formula 2 may be used singly or as the catalyst systemincluding the cocatalyst. In particular, because highly active ethyleneoligomerization reaction is possible, low-density polyethylene can beprepared in one reactor using a small amount of comonomers or using onlyethylene without comonomers.

Catalyst System

The catalyst system of the present invention includes i) a ligandcompound represented by the following Chemical Formula 1 and a chromiumsource, or ii) a chromium compound represented by the following ChemicalFormula 2; and a cocatalyst.

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other,and each independently a hydrogen atom, a hydrocarbyl group having 1 to30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbonatoms, and

X is a halogen atom or an alkyl group having 1 to 6 carbon atoms.

Detailed descriptions and preferred examples of R₁, R₂, R₂′, R₃ and X ofChemical Formulae 1 and 2 are the same as in the descriptions of theligand compound and the chromium compound of the present invention.

The catalyst system can be used in polymerization reaction ofpolyolefin, in particular, polyethylene, including ethyleneoligomerization reaction.

As used herein, the term “catalyst system” means an active catalyticcomposition that can be obtained by adding three components of thechromium source, the ligand compound and the cocatalyst or alternativelytwo components of the chromium compound and the cocatalyst at the sametime, or sequentially in any order in the presence or absence of anyproper solvent in the presence or absence of monomers. The threecomponents or two components of the catalyst system can be used withoutbeing supported on a support, or if necessary, they can be supported onthe support to be used. That is, the catalyst system according to thepresent invention includes the ligand compound represented by ChemicalFormula 1 and the chromium source, or the chromium compound representedby Chemical Formula 2 and the cocatalyst.

According to one embodiment of the present invention, the chromiumsource may be chromium or a chromium precursor. Specific examples of thechromium or chromium precursor may includechromium(III)acetylacetonoate, tris(tetrahydrofuran)chromium trichlorideor chromium(III)-2-ethylhexanoate, but the present invention is notlimited thereto.

In the catalyst system of the present invention, the cocatalyst may bean organic metal compound containing the Group 13 metal. The organicmetal compound containing the Group 13 metal is not particularlylimited, as long as it can be generally used in olefin polymerization inthe presence of a catalyst of a transition metal compound.

Specifically, the cocatalyst may be one or more selected from the groupconsisting of the compounds represented by the following ChemicalFormulae 3 to 5, but the present invention is not limited thereto.—[Al(R₄)—O]c-  [Chemical Formula 3]

wherein R₄ is the same as or different from each other, and eachindependently a halogen radical, a hydrocarbyl radical having 1 to 20carbon atoms, a halogen-substituted hydrocarbyl radical having 1 to 20carbon atoms, and c is an integer of 2 or more,D(R₅)₃  [Chemical Formula 4]

wherein D is aluminium or boron, R₅ is hydrocarbyl having 1 to 20 carbonatoms or halogen-substituted hydrocarbyl having 1 to 20 carbon atoms,[L-H]⁺[Q(E)₄]⁻  [Chemical Formula 5]

wherein L is a neutral Lewis base, [L-H]⁺ is a Bronsted acid, Q is boronor aluminium in the +3 oxidation state, E is each independently an arylgroup having 6 to 20 carbon atoms or an alkyl group having 1 to 20carbon atoms in which one or more hydrogen atoms are substituted orunsubstituted with halogen, hydrocarbyl having 1 to 20 carbon atoms, analkoxy functional group or a phenoxy functional group.

Examples of the compound represented by Chemical Formula 3 may includemethylaluminoxane (MAO), ethyl aluminoxane, isobutyl aluminoxane, butylaluminoxane or the like.

Examples of the alkyl metal compound represented by Chemical Formula 4may include trimethylaluminium, triethylaluminium, triisobutylaluminium,tripropylaluminium, tributylaluminium, dimethylchloroaluminium,dimethylisobutylaluminium, dimethylethylaluminium,diethylchloroaluminium, triisopropylaluminium, tri-s-butylaluminium,tricyclopentylaluminium, tripentylaluminium, triisopentylaluminium,trihexylaluminium, ethyldimethylaluminium, methyldiethylaluminium,triphenylaluminium, tri-p-tolylaluminium, dimethylaluminiummethoxide,dimethylaluminiumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron, tributylboron or the like.

Examples of the compound represented by Chemical Formula 5 may includetriethylammoniumtetraphenylboron, tributylammoniumtetraphenylboron,trimethylammoniumtetraphenylboron, tripropylammoniumtetraphenylboron,trimethylammoniumtetra(p-tolyl)boron,tripropylammoniumtetra(p-tolyl)boron,triethylammoniumtetra(o,p-dimethylphenyl)boron,trimethylammoniumtetra(o,p-dimethylphenyl)boron,tributylammoniumtetra(p-trifluoromethylphenyl)boron,trimethylammoniumtetra(p-trifluoromethylphenyl)boron,tributylammoniumtetrapentafluorophenylboron,N,N-diethylaniliniumtetraphenyl boron,N,N-diethylaniliniumtetraphenylboron,N,N-diethylaniliniumtetrapentafluorophenylboron,diethylammoniumtetrapentafluorophenylboron,triphenylphosphoniumtetraphenylboron,trimethylphosphoniumtetraphenylboron,triethylammoniumtetraphenylaluminium,tributylammoniumtetraphenylaluminium,trimethylammoniumtetraphenylaluminium,tripropylammoniumtetraphenylaluminium,trimethylammoniumtetra(p-tolyl)aluminium,tripropylammoniumtetra(p-tolyl)aluminium,triethylammoniumtetra(o,p-dimethylphenyl)aluminium,tributylammoniumtetra(p-trifluoromethylphenyl)aluminium,trimethylammoniumtetra(p-trifluoromethylphenyl)aluminium,tributylammoniumtetrapentafluorophenylaluminium,N,N-diethylaniliniumtetraphenylaluminium,N,N-diethylaniliniumtetraphenylaluminium,N,N-diethylaniliniumtetrapentafluorophenylaluminium,diethylammoniumtetrapentafluorophenylaluminium,triphenylphosphoniumtetraphenylaluminium,trimethylphosphoniumtetraphenylaluminium,triphenylcarboniumtetraphenylboron,triphenylcarboniumtetraphenylaluminium,triphenylcarboniumtetra(p-trifluoromethylphenyl)boron,triphenylcarboniumtetrapentafluorophenylboron or the like.

According to one embodiment of the present invention, the cocatalyst maybe alumoxane, and preferably, methyl alumoxane (MAO) as alumoxane.

According to one embodiment of the present invention, the catalystsystem may include the ligand compound represented by Chemical Formula1, the chromium source and the cocatalyst. In this regard, a molar ratioof ligand compound:chromium source:cocatalyst may be approximately 1:1:1to approximately 10:1:10,000, and preferably, approximately 1:1:100 toapproximately 5:1:3,000. When the amount of the cocatalyst is too smallto be within the range, complete activation of the catalyst does notoccur to reduce activity of the catalyst system. On the contrary, whenan excessive amount of the cocatalyst is included, excessive activatoris economically infeasible in terms of productivity or acts asimpurities to reduce purity of the product.

The catalyst system including the ligand compound represented byChemical Formula 1, the chromium source and the cocatalyst can beobtained as an active catalyst by adding three components of thecatalyst system at the same time, or sequentially in any order in thepresence or absence of monomers in any proper solvent. The propersolvent may include substituted or unsubstituted hydrocarbons having 4to 12 carbon atoms, and examples thereof may include heptane, benzene,toluene, diethyl ether, tetrahydrofuran, acetonitrile, dichloromethane,chloroform, chlorobenzene or the like, but is not limited thereto.

According to another embodiment of the present invention, the catalystsystem may include the chromium compound represented by Chemical Formula2 and the cocatalyst. In this regard, the chromium compound representedby Chemical Formula 2 and the cocatalyst may be blended in a ratio ofapproximately 1:10 to approximately 1:10,000, and preferably,approximately 1:100 to approximately 1:1,000, based on the molar ratioof chromium and metal. When the amount of the cocatalyst is too small tobe within the range, complete activation of the chromium compound doesnot occur to reduce activity of the catalyst system. On the contrary,when an excessive amount of the cocatalyst is included, excessiveactivator is economically infeasible in terms of productivity or acts asimpurities to reduce purity of the product.

The catalyst system according to the present invention can be used inethylene oligomerization reaction. That is, when ethyleneoligomerization reaction or polyolefin polymerization reaction iscarried out using the catalyst system according to the presentinvention, highly active ethylene oligomerization reaction is possible,and it is possible to polymerize low-density polyethylene in one reactorusing only ethylene without additional injection of comonomers.

MODE FOR INVENTION

Hereinafter, the present invention will be described in more detail withreference to the following Examples. However, these Examples areillustrative purposes only, and the technical scope of the presentinvention is not limited thereto.

EXAMPLE

Synthesis of Ligand Compound and Chromium Compound

Example 1 Preparation of {CH₃CH₂—S—Si(Me)₂-NH—Si(Me)₂-S—CH₂CH₃}CrCl₃[S-1 Complex] Example 1-1 Preparation of1,3-dichlorohexamethyldisilazane

15.2 g of Hexamethyldisilazane, 32.2 g of dichlorodimethylsilane, and100 mg of AlCl₃ were added to a Schlenk flask, and 150 mL ofdichloromethane was added as a solvent. The mixture was stirred at 50°C. for 3 days, and then the solvent was removed under vacuum. The crudeproduct thus obtained was subjected to fractional distillation to give acolorless product. (Yield: 80%)

1H-NMR (500 MHz, d_(δ)-benzene): δ(ppm) 1.10 (br, 1H), 0.28 (s, 12H)

Example 1-2 Preparation of CH₃CH₂—S—Si(Me)₂-NH—Si(Me)₂-S—CH₂CH₃ [S-1Ligand]

1.06 g of 1,3-dichlorohexamethyldisilazane prepared in Example 1-1, 0.72g of ethanethiol and 30 mL of THF were added to a Schlenk flask, and themixture was cooled to −78° C. Next, 1.75 mL of triethylamine was slowlyadded, and the temperature was raised to room temperature. The mixturewas stirred. After terminating the reaction, the solvent and volatilematerials were removed under vacuum. 100 mL of hexane was added to aflask and then filtered through a filter frit, and hexane was removedunder vacuum to give a light yellow liquid product. (Yield 95%)

1H-NMR (500 MHz, CDCl₃): δ(ppm) 2.56 (q, 4H), 1.30 (t, 6H), 0.39 (s,12H)

Example 1-3 Preparation of {CH₃CH₂—S—Si(Me)₂-NH—Si(Me)₂-S—CH₂CH₃}CrCl₃[S-1 Complex]

52 mg of CH₃CH₂—S—Si(Me)₂-NH—Si(Me)₂-S—CH₂CH₃ prepared in Example 1-2and 77 mg of CrCl₃(THF)₃ were added to a Schlenk flask, and 50 mL of THFwas added and stirred. The solvent was removed under vacuum to give thetitle compound as a light gray solid. (Yield 95%)

Example 2 Preparation of{CH₃(CH₂)₁₀—S—Si(Me)₂-NH—Si(Me)₂-S—(CH₂)₁₀CH₃}CrCl₃ [S-2 Complex]Example 2-1 Preparation of CH₃(CH₂)₁₀—S—Si(Me)₂-NH—Si(Me)₂-S—(CH₂)₁₀CH₃[S-2 Ligand]

1.06 g of 1,3-dichlorohexamethyldisilazane prepared in Example 1-1, 2.12g of 1-dodecanethiol and 30 mL of THF were added to a Schlenk flask, andcooled to −78° C. Next, 1.75 mL of triethylamine was slowly added, andthe temperature was raised to room temperature. Then, the mixture wasstirred. After terminating the reaction, the solvent and volatilematerials were removed under vacuum. 100 mL of hexane was added to aflask and then filtered through a filter frit, and hexane was removedunder vacuum to give a light yellow liquid product. (Yield 93%)

1H-NMR (500 MHz, CDCl₃): δ(ppm) 2.57 (q, 4H), 1.56 (q, 4H), 1.35-1.20(m, 32H), 0.86 (t, 6H), 0.40 (s, 12H)

Example 2-2 Preparation of{CH₃(CH₂)₁₀—S—Si(Me)₂-NH—Si(Me)₂-S—(CH₂)₁₀CH₃}CrCl₃ [S-2 Complex]

101 mg of CH₃(CH₂)₁₀—S—Si(Me)₂-NH—Si(Me)₂-S—(CH₂)₁₀CH₃ prepared inExample 2-1 and 60.9 mg of CrCl₃(THF)₃ were added to a Schlenk flask, 50mL of THF was added thereto and stirred. The solvent was removed undervacuum to give the title compound as a light gray solid. (Yield 90%)

Example 3 Preparation of{(2-MeO)C₆H₄—S—Si(Me)₂-NH—Si(Me)₂-S—C₆H₄(2-OMe)}CrCl₃ [S-3 Complex]Example 3-1 Preparation of(2-MeO)C₆H₄—S—Si(Me)₂-NH—Si(Me)₂-S—C₆H₄(2-OMe) [S-3 Ligand]

The compound was prepared in the same manner as in Example 2-1, exceptusing 2-methoxythiophenol instead of 1-dodecanethiol. (Yield 84%)

1H-NMR (500 MHz, CDCl₃): δ(ppm) 7.39 (q, 2H), 7.22 (q, 2H), 6.84 (m,4H), 3.83 (s, 6H), 1.25 (brs, 1H), 0.25 (s, 12H)

Example 3-2 Preparation of{(2-MeO)C₆H₄—S—Si(Me)₂-NH—Si(Me)₂-S—C₆H₄(2-OMe)}CrCl₃ [S-3 Complex]

412 mg of (2-MeO)C₆H₄—S—Si(Me)₂-NH—Si(Me)₂-S—C₆H₄(2-OMe) prepared inExample 3-1 and 377 mg of CrCl₃(THF)₃ were added to a Schlenk flask, and20 mL of THF were added and stirred. The solvent was removed undervacuum to give the title compound as a light purple solid. (Yield 85%)

Comparative Example 1 Preparation of{CH₃CH₂—S—(CH₃)₂—NH—Si(CH₃)₂—S—CH₂CH₃}CrCl₃ [T Complex]

The title compound was prepared with reference to the previouslyreported literature, J. AM. CHEM. SOC. 2003, 125, 5272-5273.

<Ethylene Oligomerization Reaction>

Example 4 Ethylene Oligomerization Reaction of S-1 Complex

The pressure of 500 ml-high pressure reaction vessel was reduced tovacuum, and then the internal environment was made to inactive conditionusing argon gas. Then, 250 ml of pure toluene was added, andmethylaluminoxane (MAO) was added 600-fold of the Al/Cr molar ratio.Subsequently, a toluene solution (5 ml, 25 μmol of S-1 complex) of 5 mMS-1 complex catalyst was added and the solution reaction was carried outat 60° C. for 1 hour under a 50 psig pressure of ethylene. Then, theactivity was calculated from the increased weight of the solution afterreaction and the weight of the reactor. The temperature of the reactorwas reduced to 0° C., and then an HCl aqueous solution was slowly addedto remove residual MAO and the catalyst. The organic layer was taken andfiltered, and the produced polymer was separated and dried. Further, theorganic layer was dried over MgSO₄ to remove the residual moisture, andthen the composition of the organic layer was identified by GC-MS. As aresult, a mixture of alpha-olefin polymers with Schultz-Florydistribution was identified.

A graph measured by GC-MS is shown in FIG. 1.

Example 5 Ethylene Oligomerization Reaction of S-1 Complex

Oligomerization reaction was carried out in the same manner as inExample 4, except that the reaction was carried out at a reactiontemperature of 90° C. in Example 4.

Example 6 Ethylene Oligomerization Reaction of S-2 Complex

Oligomerization reaction was carried out in the same manner as inExample 4, except that S-2 complex was used instead of S-1 complex inExample 4.

Example 7 Ethylene Oligomerization Reaction of S-2 Complex

Oligomerization reaction was carried out in the same manner as inExample 4, except that S-2 complex was used instead of S-1 complex andthe reaction was carried out at a reaction temperature of 90° C. inExample 4.

Example 8 Ethylene Oligomerization Reaction of S-3 Complex

Oligomerization reaction was carried out in the same manner as inExample 4, except that S-3 complex was used instead of S-1 complex inExample 4.

Example 9 Ethylene Oligomerization Reaction of S-3 Complex

Oligomerization reaction was carried out in the same manner as inExample 4, except that S-3 complex was used instead of S-1 complex andthe reaction was carried out at a reaction temperature of 90° C. inExample 4.

Example 10 Ethylene Oligomerization Reaction using S-1 Ligand Compoundand Chromium Source

The pressure of 500 ml-high pressure reaction vessel was reduced tovacuum, and then the internal environment was made to inactive conditionusing argon gas. Then, 250 ml of pure toluene was added, andmethylaluminoxane (MAO) was added 600-fold of the Al/Cr molar ratio.Subsequently, a toluene solution (5 mM, 25 μmol) of 5 mM S-1 ligandcompound of Example 1-2, 9.4 mg (25 μmol) of CrCl₃(THF₃), and 5 mL oftoluene were added to a 50 mL Schlenk flask, and stirred at roomtemperature for 5 minutes, and then added to a reactor. The solutionreaction was carried out at 90° C. for 1 hour under a 50 psig pressureof ethylene. Then, the activity was calculated from the increased weightof the solution and the weight of the reactor. The temperature of thereactor was reduced to 0° C., and then an HCl aqueous solution wasslowly added to remove residual MAO and the catalyst. The organic layerwas taken and filtered, and the produced polymer was separated anddried. Further, the organic layer was dried over MgSO₄ to remove theresidual moisture, and then the composition of the organic layer wasidentified by GC-MS. As a result, a mixture of alpha-olefin polymerswith Schultz-Flory distribution was identified.

Example 11 Ethylene Oligomerization Reaction using S-2 Ligand Compoundand Chromium Source

Oligomerization reaction was carried out in the same manner as inExample 10, except that S-2 ligand compound was used instead of S-1ligand compound in Example 10.

Example 12 Ethylene Oligomerization Reaction using S-3 Ligand Compoundand Chromium Source

Oligomerization reaction was carried out in the same manner as inExample 10, except that S-3 ligand compound was used instead of S-1ligand compound in Example 10.

Comparative Example 2

Oligomerization reaction was carried out in the same manner as inExample 4, except that T complex of Comparative Example 1 was usedinstead of S-1 complex and the reaction was carried out at a reactiontemperature of 90° C. in Example 4.

The results of ethylene oligomerization reaction of Examples 4 to 12 andComparative Example 2 are shown in Table 1.

TABLE 1 Reaction temperature Activity Catalyst (unit: ° C.) (unit: g/gof Cr/hr) Example 4 S-1 complex 60 13,850 Example 5 S-1 complex 90 9,540Example 6 S-2 complex 60 29,160 Example 7 S-2 complex 90 19,341 Example8 S-3 complex 60 7,615 Example 9 S-3 complex 90 1,923 Example 10 S-1ligand/chromium 90 9,120 source Example 11 S-2 ligand/chromium 90 20,301source Example 12 S-3 ligand/chromium 90 1,510 source Comparative Tcomplex 90 2,510 Example 2

Referring to Table 1, when ethylene oligomerization reaction was carriedout using the catalyst system including the compound of the presentinvention, highly active ethylene oligomerization reaction was possible.

Referring to FIG. 1, when ethylene oligomerization reaction according toone embodiment of the present invention was carried out, it was foundthat alpha-olefin polymer products were obtained in the form of mixtureaccording to Schultz-Flory distribution.

The invention claimed is:
 1. A ligand compound represented by the following Chemical Formula 1:

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other, and each independently a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbon atoms.
 2. The ligand compound according to claim 1, wherein R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkylaryl group having 7 to 12 carbon atoms, an arylalkyl group having 7 to 12 carbon atoms or an alkoxyaryl group having 7 to 12 carbon atoms.
 3. The ligand compound according to claim 1, wherein R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, a linear alkyl group having 1 to 20 carbon atoms, an isopropyl group, a tert-butyl group, an amyl group, a phenyl group, an alkylphenyl group having 7 to 12 carbon atoms or an alkoxyphenyl group having 7 to 12 carbon atoms.
 4. The ligand compound according to claim 1, wherein the compound represented by Chemical Formula 1 is one of the following chemical structures:


5. A chromium compound represented by the following Chemical Formula 2:

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other, and each independently a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbon atoms, and X is a halogen atom or an alkyl group having 1 to 6 carbon atoms.
 6. The chromium compound according to claim 5, wherein R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkylaryl group having 7 to 12 carbon atoms, an arylalkyl group having 7 to 12 carbon atoms or an alkoxyaryl group having 7 to 12 carbon atoms.
 7. The chromium compound according to claim 5, wherein R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, a linear alkyl group having 1 to 20 carbon atoms, an isopropyl group, a tert-butyl group, an amyl group, a phenyl group, an alkylphenyl group having 7 to 12 carbon atoms or an alkoxyphenyl group having 7 to 12 carbon atoms.
 8. The chromium compound according to claim 5, wherein X is Cl or a methyl group.
 9. The chromium compound according to claim 5, wherein the compound represented by Chemical Formula 2 is one of the following chemical structures:


10. A catalyst system comprising i) a ligand compound represented by the following Chemical Formula 1 and a chromium source, or ii) a chromium compound represented by the following Chemical Formula 2; and a cocatalyst:

wherein R₁, R₂, R₂′ and R₃ are the same as or different from each other, and each independently a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a heterohydrocarbyl group having 1 to 30 carbon atoms, and X is a halogen atom or an alkyl group having 1 to 6 carbon atoms.
 11. The catalyst system according to claim 10, wherein R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkylaryl group having 7 to 12 carbon atoms, an arylalkyl group having 7 to 12 carbon atoms or an alkoxyaryl group having 7 to 12 carbon atoms.
 12. The catalyst system according to claim 10, wherein R₁, R₂, R₂′ and R₃ are each independently a hydrogen atom, a linear alkyl group having 1 to 20 carbon atoms, an isopropyl group, a tert-butyl group, an amyl group, a phenyl group, an alkylphenyl group having 7 to 12 carbon atoms or an alkoxyphenyl group having 7 to 12 carbon atoms.
 13. The catalyst system according to claim 10, wherein X is Cl or a methyl group.
 14. The catalyst system according to claim 10, wherein chromium source is selected from the group consisting of chromium(III)acetylacetonoate, tris(tetrahydrofuran)chromium trichloride, and chromium(III)-2-ethylhexanoate.
 15. The catalyst system according to claim 10, wherein the cocatalyst is one or more selected from the group consisting of the compounds represented by the following Chemical Formulae 3 to 5: —[Al(R₄)—O]c-  [Chemical Formula 3] wherein R₄ is the same as or different from each other, and each independently a halogen radical, a hydrocarbyl radical having 1 to 20 carbon atoms, a halogen-substituted hydrocarbyl radical having 1 to 20 carbon atoms, and c is an integer of 2 or more, D(R₅)₃  [Chemical Formula 4] wherein D is aluminium or boron, R₅ is hydrocarbyl having 1 to 20 carbon atoms or halogen-substituted hydrocarbyl having 1 to 20 carbon atoms, [L-H]⁺[Q(E)₄]⁻  [Chemical Formula 5] wherein L is a neutral Lewis base, [L-H]⁺ is a Bronsted acid, Q is boron or aluminium in the +3 oxidation state, E is each independently an aryl group having 6 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms in which one or more hydrogen atoms are substituted or unsubstituted with halogen, hydrocarbyl having 1 to 20 carbon atoms, an alkoxy functional group or a phenoxy functional group.
 16. The catalyst system according to claim 10, wherein the catalyst system is used in ethylene oligomerization reaction. 